Morphologic study of squirrel monkey placentation was done to determine if gross and microscopic abnormalities were associated with and predictive for negative fetal outcomes such as abortion and neonatal death. Fourteen complete placentas and 6 partial placentas were recovered from abortions, stillbirths, and live births. Placentas were weighed immediately, photographed, evaluated for gross lesions and sections collected for histopathology and frozen in liquid nitrogen. Three microscopic lesions have been found to be predictive for fetal/infant death: acute suppurative inflammation, nonsuppurative inflammation associated with Encephalitozoon infection, and extensive placental infarction. Microscopic evaluation of the placenta is particularly helpful when there is no fetal tissue or when lesions in the fetus are not diagnostic.